Motorized joint

ABSTRACT

The invention provides a motorized joint which has a pair of members that are movable relative to one another about a joint. Power to actuate the joint is provided by an inflatable hose inflating to transmit the force due to the expansion thereof via a strap or other elements interconnecting the members. The motorized joint can be covered with artificial flesh which, together with the expansion of the inflatable hose, creates the realistic appearance of a muscle flexing.

The present invention relates to a motorized joint for producing therealistic appearance and action of animal or human muscles in artificiallimbs.

Artificial limbs are commonly prepared for amputees and people havingcomparable disabilities. Unfortunately, such limbs are rarelyattractive, and fail to reproduce the appearance of the limbs they areintended to replace. This can have adverse psychological effects on thewearers of the limbs.

Additionally, the limbs are increasingly required as constituent partsof experimental and industrial robots, and there is a growing range ofapplications of artificial limbs in high technology animated televisionand cinema productions. Further, successful television and filmrecordings encourage secondary markets in the merchandising of souvenirmodels of characters appearing in such productions. It has been a longstanding problem that, in order to manufacture the souvenir modelssufficiently cheaply to exploit the intended market for them, the modelsdo not accurately reproduce the appearance or actions of the charactersupon which they are based.

Accordingly, the present invention provides A motorized joint in askeleton structure comprising a pair of relatively movable limbs, aninflatable element having an inextensible wall acting between the limbs,means to interconnect the inflatable element to the limbs such that inone position of relative movement of the limbs the element is in adeflated, flat and folded condition and means to inflate the elementcausing the element to increase in cross-section and unfold to causerelative movement between the limbs from said one position to a furtherposition of relative movement.

Such a motorized joint as defined above is characterized by a lack ofinternal inertia. This is brought about by the low level of internalfriction in the motorized joint which may be pneumatically orhydraulically controlled. Thus, the problems, evident in previousjoints, associated with the transition from static to dynamic friction(which is known as "break out" in the art) are absent from motorizedjoints according to the present invention. This solves a problem withprevious artificial limbs that the movement of the limb is unnatural inappearance due to jerking of the joint as the inertia of previousmotorized actuators is overcome. The movement of a motorized joint ofthe present invention is, by contrast, smooth and progressive and can beaccurately controlled by a proportional controller, again enhancing thelife-like nature of the movement of the muscle.

Further, a skeletal structure comprising a motorized joint according tothe invention and a plurality of interconnected, further elements willhave a realistic animal-like motion, since movement in one part of theskeleton will result in corresponding reactions elsewhere in thestructure due to the interconnection of the elements thereof.

A further advantage of using an inflatable element to apply the forcerequired to move the relatively movable limbs, which represent orreplace the bones of the limb under consideration, is that the expansionof the inflatable element which accompanies the operation of the jointreproduces the action of an animal or human muscle, which enlarges whenthe muscle is flexed. Additionally, a motorized joint which incorporatesan inflatable element to produce an actuating force requires fewerprecision-manufactured components than previous artificial joints, andconsequently is cheaper to manufacture and maintain than such previousdesigns. Such a joint is also quiet in operation.

Preferably, the relatively movable limbs are interconnected by a hingedjoint. This feature permits the use of the motorized joint of theinvention in artificial limbs designed to reproduce the appearance andfunction of actual animal and human joints.

Alternatively, the present invention provides a motorized joint in askeleton structure comprising a pair of relatively movable limbs, aninflatable element having an inextensible wall acting between the limbs,means to interconnect the inflatable element to the limbs such that inone position of relative movement of the limbs the element is in adeflated, flat and folded condition and means to inflate the elementcausing the element to increase in cross-section and to unfold to causerelative movement between the limbs from said one position to a furtherposition of relative movement, wherein the relatively movable limbs areinterconnected by a framework. The advantage of this arrangement isthat, in certain cases in human and animal skeletons, a complicatedarray of bones exists to effect a particular movement, such as rotationof the human arm about the shoulder joint. The use of a framework tolocate the relatively movable limbs of the powered joint of theinvention permits a reduction of the number of relatively movablecomponents required to create the movement, and consequently simplifiesthe design of the joint.

Instead of the arrangements defined above, the present inventionprovides a motorized joint in a skeleton structure comprising a pair ofrelatively movable limbs, an inflatable element having an inextensiblewall acting between the limbs, means to interconnect the inflatableelement to the limbs such that in one position of relative movement ofthe limbs the element is in a deflated, flat and folded condition andmeans to inflate the element causing the element to increase incross-section and to unfold to cause relative movement between the limbsfrom said one position to a further position of relative movement,wherein the relatively movable limbs are interconnected by a jointpermitting relative rotation between said members.

Preferably, the inflatable element in any of the arrangements definedhereinabove acts directly between the relatively movable limbs.

Conveniently, the inflatable element comprises a length of inflatable,hollow hose sealed at one end thereof and having a generally flattransverse cross-section when in a deflated, unfolded state.

Further, it is preferable that the inflatable hose comprises meansseparating the opposing inner faces of said hose at the fold therein,thereby permitting passage of fluid between the two portions of the hoserespectively on either side of said fold. Conveniently, the meansseparating the opposing inner faces of the hose comprises a length offlat, flexible, moulded plastic netting of narrower width than theinterior transverse dimension of said hose, said netting being insertedlengthwise in said hose to maintain separation of the opposing faces ofsaid hose on folding thereof.

Preferably the means to supply fluid under pressure to the inflatableelement comprises a fluid supply pipe retained in the aperture at theopen end of the inflatable hose, at least one sealing block adapted sealsaid end of the inflatable hose having the fluid supply pipe retainedtherein, clamping means to press said sealing block into contact withsaid end of the hose against a reaction surface also adapted toaccommodate said end of the hose, pressurized fluid supply meansselectively connectable to said supply pipe to supply inflating fluidthereto, and venting means selectively connectable to said supply pipefor use in deflating said inflatable hose.

According to a further preferred aspect of the present invention, themeans to interconnect the inflatable element to the relatively movablelimbs comprises clamping means securing the inflatable element to atleast one of said relatively movable limbs.

Preferably, the means to interconnect the inflatable element to therelatively movable limbs comprises clamping means securing theinflatable element respectively to each relatively movable limb.

Alternatively, it is preferable that the means to interconnect theinflatable element to the relatively movable limbs comprises a flexiblestrap secured at each end thereof respectively to a relatively movablelimb, the inflatable element being so disposed that, on inflationthereof, the force created in said inflatable element bears against saidflexible strap, thereby creating tension in said flexible strap andoccasioning movement between the relatively movable limbs.

A further preferable aspect of the invention is that the meansinterconnecting the inflatable element to the relatively movable limbscomprises a bearing surface disposed on one of said limbs, against whichbearing surface the force created on inflation and deflation of theinflatable element reacts to magnify the relative movement of the limbsfor a given inflation of said inflatable element.

Preferably, the motorized joint of the invention further comprisesspring means interconnecting the relatively movable limbs which springmeans, on deflation of the inflatable element, cause reversal of themovement between the relatively movable members.

In accordance with a preferable aspect of the invention, there isprovided a motorized joint as defined hereinabove comprising artificialflesh surrounding said joint such that the joint resembles an animaljoint and reproduces the appearance of the flexing of an animal muscleon inflation of the inflatable element.

Preferably, the motorized joint as defined herein comprises a pluralityof pivotal axes and a corresponding plurality of inflatable elements.

In one aspect, the invention provides a skeletal structure having amultiplicity of motorized joints each as defined herein, wherein eachjoint comprises a corresponding multiplicity of inflatable elements.

According to yet a further preferable aspect of the invention, there isprovided a pneumatic circuit comprising a plurality of motorized jointseach as defined hereinabove.

In yet a further preferable aspect of the invention, there is provided ahydraulic circuit comprising a plurality motorized joints each asdefined hereinabove.

There now follows a description of a number of specific embodiments ofthe invention, reference being made to the accompanying drawings inwhich:

FIG. 1 is a side elevational view of a motorized joint comprising afirst preferred embodiment of the invention;

FIG. 2 is a cross-sectional view of apparatus according to the presentinvention for permitting inflation of an inflatable element thereof;

FIG. 3 is a perspective view of a sealing block for use in the apparatusof FIG. 2;

FIG. 4 is a cross-sectional view of apparatus to be used as analternative to that shown in FIG. 2;

FIG. 5 is a perspective view of a sealing block for use in the apparatusof FIG. 4;

FIG. 6 is a side elevational view of a motorized joint comprising asecond preferred embodiment of the invention;

FIG. 7 is a front elevational view of a motorized joint comprising athird preferred embodiment of the invention;

FIG. 8 is a cross-sectional view of the artificial joint of FIG. 7;

FIG. 9 is a perspective view of a motorized joint comprising a furtherpreferred embodiment of the invention;

FIGS. 10 and 11 are a top plan view and a longitudinal cross sectionalview respectively of a motorized joint comprising a fifth preferredembodiment of the present invention;

FIG. 12 is a perspective view of a length of inflatable hose for use inthe embodiments of the invention described herein;

FIGS. 13 to 15 are schematic views of hydraulic or pneumatic circuitscomprising motorized joints each according to the present invention.

Referring firstly to FIG. 1, there is shown a side elevational view of asimple motorized joint in an artificial limb in accordance with a firstpreferred embodiment of the invention.

The motorized joint comprises a first skeletal limb 1 of hollow,generally circular transverse cross-section hingedly connected by a pinjoint to be described below to a second skeletal limb 3, which is alsoof hollow, generally circular transverse cross section. In the region ofthe pin joint, the cross sections of skeletal limbs 1, 3 are adapted toaccommodate the pin joint. In the region referred to, skeletal limb 1comprises two flattened forward-protruding lugs of which only one,indicated at 4 in FIG. 1, is visible in FIG. 1. Flattened lugs 4 arerespectively disposed parallel to one another on opposite sides of thecircumference of cylindrical limb 1 and have generally parallel innerfaces. A through-bore 5 on a respectively common axis 8 passes throughboth lugs 4. Lugs 4 lie spaced apart from one another in the directionof the common axis. In the region of pin joint 12, second skeletal limb3 comprises a single, flattened, forwardly protruding lug 6 disposedgenerally diametrically across the circular cross section of secondskeletal limb 3 and having a through-bore on an axis common with axis 8passing through lugs 4 referred to above. The width of lug 6 measured inthe direction of axis 8 is smaller than the distance separating theparallel lugs 4. Lug 6 is disposed to lie in the axial space between thelugs 4. A pin 10 fixed at either end respectively to the lugs at theouter ends of the through-bore 5 therethrough passes through thethrough-bore in lug 6 referred to above. Pin 10 is a loose fit in thethrough-bore in lug 6, and thereby serves to locate lug 6 and skeletallimb 3 such that skeletal limbs 1 and 3 are rotatable relative to oneanother about axis 8 as indicated by the arrow A in FIG. 1. Thus thejoint interconnecting skeletal limbs 1 and 3 in FIG. 1 is a movable pinjoint, referred to generally at 12.

Interconnecting skeletal limbs 1 and 3 about the obtuse angle formed inthe pin joint 12 is an inflatable element 14 formed as an inflatablehose 16. Inflatable hose 16 is secured at one end 18 to skeletal limb 3by clamping means 20 to be described below and at the opposite end 19thereof to skeletal member 1 by further clamping means 22.

The clamping means 20 secures the end 18 of inflatable hose 16 againstmovement relative to skeletal limb 3, and also seals the end 18 in anair-tight closure.

Clamping means 22 secures the end 19 of inflatable hose 16 againstmovement relative to skeletal limb 1 and also secures air supply andvent pipe 24, in a manner to be described below. Air supply and ventpipe 24 communicates with the interior of inflatable hose 16 and isretained in an air-tight joint such that pipe 24 is the only passagethrough which air may enter and leave inflatable hose 16. Air supply andvent pipe 24 is selectively connectable to a pressurized air supplysource and a deflating vent arrangement respectively. In practice, theair supply source and vent are selectively connected to air supply pipe24 by a multi-port solenoid operated control valve or similar means,which valve may be controllable by a hydraulic or pneumatic circuit, bymanual operation or by computer.

Skeletal limb 3 comprises a moulded bearing pad 26 which may be of asuitable, hard plastic and which is formed as or rigidly secured to anupper portion of the member 3 such that inflatable hose 16 bears againstthe surface of bearing pad 26. In use, to operate the motor drivenjoint, air supply pipe 24 is connected to a pressurized air supplysource (not shown) which therefore inflates hose 16 with pressurizedair. As hose 16 inflates it tends to shorten the distance between theends 18, 19 thereof and consequently operate joint 12 in the directionof arrow B by virtue of clamping means 20 and 22 transmitting the forcesthus created in hose 16 to skeletal limbs 1 and 3 simultaneously. Thiseffect is enhanced by the action of hose 16 against bearing pad 26 asthe diameter of hose 16 increases on inflation, and is further enhancedby the fact that hose 16 is initially manufactured as a straight tube.When the artificial muscle is in a relaxed state, as is shown in FIG. 1,hose 16 is curved or folded about a transverse axis thereof. However, oninflation of hose 16 to activate the motor driven joint, hose 16 tendsto return to the straight, as manufactured state thereof, and thiseffect enhances the effect of operating pin joint 12 in the direction ofarrow B.

An effect which accurately reproduces the flexing of an animal muscle isobserved in the inflatable hose 16 on inflation thereof, since theexpansion of the hose 16 resembles that of an animal muscle duringtensing or flexing thereof.

The motor driven joint of FIG. 1 may be operated in reverse byconnecting air supply and vent pipe 24 to air vent means (not shown)again in practice by use of solenoid actuated control valves or similarmeans. This causes inflatable hose 16 to deflate on venting thereof,thereby causing hose 16 to revert to the deflated configurationdescribed above. This deflating of hose 16 induces in the clamping means20, 22 securing the ends 18, 19 respectively of inflatable hose 16forces which act in generally the opposite directions to those incurredduring inflation of the inflatable hose 16 and consequently cause themotorized joint to operate in the sense indicated by arrow C in FIG. 1.

However, it has been found that, while the forces referred to as actingon deflation of inflatable hose 16 are sufficient to operate themotorized joint of FIG. 1 in the direction of arrow C, such forces asare produced are not as great as those which act on inflation ofinflatable hose 16. Thus, in particular situations including those wherethe motorized joint of FIG. 1 is to be included in a limb prosthesis fora disabled person, it may be necessary for the embodiment of theinvention, shown in FIG. 1 to include a return spring 500 or similardevice interconnecting the skeletal limbs 1, 3 across the acute angleformed therebetween. In such a case, inflation of inflatable hose 16will always take place against the influence of the spring andconsequently higher fluid pressures may be required for operation of themotorized joint. The return spring 500 may be in the form of a tensionspring, elasticized members or the like.

Referring now to FIGS. 2 and 3 of the drawings there is shown anarrangement for clamping the inflatable element 14 of FIG. 1 to askeletal limb while simultaneously sealingly retaining in an aperturethereof the fluid supply pipe 24 of FIG. 1. The arrangement of FIGS. 2and 3 is therefore suitable for performing the function of the clampingmeans 22 shown in FIG. 1.

FIG. 2 is a cross-sectional view of a portion of limb 1 of FIG. 1 alonglines X--X showing the region of the limb where inflatable hose 16 issecured to limb 1.

Limb 1 is shown as a hollow circular member secured to which is hose 16having supply and vent pipe 24 inserted therein. Supply and vent pipe 24is retained in the open end of hose 16 as shown by an adhesive compound.The adhesive compound serves to prevent the supply and vent pipe 24 fromfalling out of inflatable hose 16 during assembly of the motor drivenjoint. Disposed above inflatable hose 16 as shown in FIG. 2 is sealingblock 30 which is shown in perspective view in FIG. 3. Sealing block 30is generally curved in a transverse axial direction to enable a closefit between the inner surface 32 thereof and the upper surface 34 ofinflatable hose 16 at the point of securing of the hose. Outer surface36 of sealing block 30 is of generally similar curvature to that ofinner surface 32. A longitudinally axial channel 38 of semi-circularcross section extends along the length of the inner surface 32 ofsealing block 30. When sealing block 30 is positioned on inflatable hose16, channel 38 mates with a raised portion in the upper surface 34 ofinflatable hose 16 which raised portion is caused by the presence ofsupply and vent pipe 24 retained in the open end of hose 16 causing abulge in the upper surface 34 thereof.

In use, sealing block 30 is forced down onto hose 16 against skeletallimb 1 by a clamping clip 39 which passes around sealing block 30 andlimb 1 enclosing block 30, limb 1, hose 16 and pipe 24 within thecircumference thereof. Clamping clip 39 applies a significant force tosealing block 30 with the effects of sealing the open end of hose 16about supply and vent pipe 24 against fluid flow; enhancing theretention of pipe 24 within the end of hose 16; and securing inflatablehose 16 against movement relative to skeletal limb 1.

Clamping clip 39 may conveniently comprise a worm-drive hose clip.

An alternative to the arrangement shown in FIGS. 2 and 3 is depicted inFIGS. 4 and 5, which depict an arrangement for securing an inflatableelement 14 in accordance with the invention to a skeletal limb 40 ofgenerally flat surface contour.

FIG. 4 represents a comparable view of skeletal limb 40 to that shown oflimb 1 in FIG. 2. Inflatable element 14 has an open end in which supplyand vent pipe 24 is retained. Inflatable element 14 is secured to limb40 and sealed around pipe 24 and at the open end thereof by the actionof sealing block 42 pressing the end of inflatable member 14 against theupper surface 44, as shown in FIG. 4, of limb 40. Sealing block 42, asshown in FIG. 5, is of generally rectangular prismatic form having achannel 46 of generally semi-circular cross section formed therein. Asin the arrangement shown in FIGS. 2 and 3, the semi-circular channel 46mates with the bulge formed in the upper surface 48 of inflatableelement 14 by the retention of pipe 24 within the open end of element14. Sealing block 42 is pressed into contact with inflatable element 14by shim 49 which in turn is clamped against sealing block 42 by nut andbolt assemblies 50 which secure the sealing arrangement to limb 40.

It will be clear that the sealing arrangements described above andillustrated in FIGS. 2 to 5 inclusive may be used for securing andsealing the ends of inflatable elements of the invention from whichsupply and vent pipes 24 are absent. In such cases, the sealing blocks30 and 42 are not provided with semi-circular channels 38 and 46respectively. It is necessary to seal inflatable elements 14 not havingsupply and vent pipes 24 when the inflatable element has been formed asa length of inflatable hose. In the embodiment of the inventiondescribed hereinabove, and in further embodiments to be described below,it is necessary both to secure and seal the opposite end of aninflatable hose to that having a supply and vent pipe retained therein.In such cases, such sealing blocks not having semi-circular channels areemployed.

Folded inflatable hose 16 has inserted therein along the length thereofand around the fold a flat, flexible sheet of nylon mesh netting 15,such as the proprietary product "NETLON", which name is believed to be aRegistered Trade Mark. The purpose of having a sheet of "NETLON" (shownby dotted lines in FIG. 1) inserted in particular about the fold in hose16 is to ensure that, on inflation of hose 16, the opposing interiorfaces of the hose 16 at the point of folding do not seal the hose acrossthe fold. This feature prevents a pocket of air from becoming trapped ina portion of hose 16 on deflation thereof.

Turning now to FIG. 6, there is shown a second preferred embodiment ofthe present invention comprising a pair of relatively movable, hollow,circular skeletal limbs 60, 61 interconnected by a movable pin joint 62similar to pin joint 12 shown in FIG. 1.

Inflatable element 14 is an inflatable hose 64 which is doubled backupon itself to lie as a folded hose on bearing pad 67 of limb 61. Bothends 65, 66 of inflatable hose 64 are both sealed and clamped to limb 61by a single clamping arrangement 68 which is similar to that describedwith reference to FIGS. 2 and 3 above. End 65 of inflatable hose 64 hasretained and sealingly clamped therein a fluid supply and vent pipe 70which is selectively connectable either to a source of pressurized airor a venting arrangement.

A flexible, inextensible strap 72 is secured at one end thereof inclamping arrangement 68 and extends from clamping arrangement 68 alongthe upper folded portion, as shown in FIG. 6, of inflatable hose 64. Atthe point on folded inflatable hose 64 where the curvature thereofbecomes too great, due to the folding, for flexible strap 72 to remainin contact with the surface of the hose 64, flexible strap 72 breaksaway from the surface of hose 64 and extends forwardly thereof to passthrough hasp 74 and is firmly secured to skeletal limb 60 by furtherclamping means 76. Clamping means 76 comprises a screw and washerassembly, the screw 78 being screwed into skeletal limb 60 to causewasher 79 to grip flexible strap and prevent relative movement betweenthe limb 60 and strap 72. Hasp 74 comprises a rigid or semi-rigid loopsecured at a lower end thereof to limb 61, and through which loopflexible strap 72 passes as indicated above. In use, hasp 74 serves as areaction member against which the tension to be created in flexiblestrap 72 reacts.

In use, the embodiment of the invention shown in FIG. 6 operates to movethe skeletal limbs 60 and 61 in the sense of arrow A on inflation offolded, inflatable hose 64 and in the sense of arrow B on deflation ofinflatable hose 64.

Inflation of inflatable hose 64 is occasioned by the selectiveconnection, by virtue of solenoid operated pneumatic control valves, orsimilar means, of air supply and vent pipe 70 to a source of pressurizedair (not shown). Air thus flows in to inflatable hose 64 and the effectsof the expansion of hose 64; the reaction of hose 64 against strap 72and the bearing surface 67 of limb 61; and the tendency of folded,inflatable hose 64 to unfold on inflation thereof combine to producesignificant tension in flexible strap 72. The force in flexible strap 72reacts at clamping arrangement 68, hasp 74 and clamping means 76 tocause relative axial movement of the limbs 60, 61 in the direction ofarrow A in FIG. 6. The action of the motorized joint of FIG. 6 isbroadly similar to that of FIG. 1.

On deflation of inflatable hose 64, deflation being caused by selectiveconnection of supply and vent pipe 70 to a venting arrangement (notshown) the hose 64 reverts to the deflated state thereof as a foldedhose lying along skeletal limb 61. The self-weight of skeletal members60 and 61 acting during deflation against the resilience of flexiblestrap 72 is generally sufficient to cause relative movement of skeletallimbs 60 and 61 in the sense of arrow B in FIG. 6, but it may benecessary to provide a spring 501 to interconnect limbs 60 and 61 acrossthe acute angle subtending therebetween and provide an additional returnforce in the powered joint.

Deflation of hose 64 is assisted, as in the embodiment of FIG. 1, by thepresence of a sheet 71 of "NETLON" or similar material to preventaccidental sealing of the hose across the fold therein.

The embodiments of the invention described with reference to FIGS. 1 and6 above are of particular use in the construction of motorized knee andelbow joints in artificial limbs for use in models, animated puppets andsurgical prostheses.

Referring now to FIGS. 7 and 8 there is shown a third preferredembodiment of the present invention.

This third embodiment of the invention is of use in the construction ofmotorized artificial shoulder and neck joints, and has applications inthe fields of modelmaking and animated puppet manufacture.

FIG. 7 is a front elevational view of a motorized joint comprising anoutput shaft 80 which is to undergo controlled rotation in relation to asupport framework 82 and fixed cylindrical skeletal limb 83. Outputshaft 80 is formed as an axial extension of circular, skeletal limb 84which is rotatable in bearings 85, 86 shown schematically in FIG. 7disposed at, and supporting either end of rotatable limb 84. Bearings85, 86 are mounted in frame members 82 which are interconnected by fixedlimb 83, which limb is disposed to be generally parallel to rotatablelimb 84.

Referring to FIG. 8, there is shown a cross-sectional view taken alongthe line Y--Y of FIG. 7, and showing the motor driven joint in greaterdetail.

A clamping arrangement 90 comprising screws 91 and a sealing block 92 ofa type similar to that shown in FIG. 5 is shown in FIG. 8 at a pointapproximately 135° from the top dead center of fixed cylindrical limb 83when measured in a clockwise sense. Sealing block 92 differs slightlyfrom that shown in FIG. 5 since it is contoured to be a close fit on thesurface of cylindrical, fixed limb 83.

Sealing block 92 is screwed into cylindrical fixed skeletal limb 83 atthe position indicated and serves to clamp in position and seal bothends 93, 94 of an inflatable member 14 in the form of an inflatable hose95 which is folded back on itself and is curved partially around limb 83as shown in FIG. 8.

Sealing block 92 also secures air supply and vent pipe 97 to end 93 andwhich communicates with the interior of hose 95 and is selectivelyconnectable to either a pressurized air supply source (not shown) or aventing arrangement for inflation and venting of the inflatable hose 95.

Sealing block 92 also serves to clamp flexible strap 100 at one endthereof. Flexible strap 100 extends of sealing block 92 about the outersurface contour of inflatable hose 95 as it lies about limb 83 andfurther extends forwardly thereof to contact the circumference ofrotatable cylindrical limb 84 and follow said circumference to a pointmeasured approximately, 135° clockwise rotation from the top dead centerof limb 84 where the end of flexible strap 100 is clamped to limb 84 bya clamping arrangement 101 similar to those previously described.

Folded inflatable hose 95 has inserted therein along the length thereofand around the fold a flat, flexible sheet of nylon mesh netting 102,such as the proprietary product "NETLON", which name is believed to be aRegistered Trade Mark. The purpose of having a sheet of "NETLON" (shownby dotted lines in FIG. 8) inserted in particular about the fold in hose95 is to ensure that, on inflation of hose 95, the opposing interiorfaces of the hose 95 at the point of folding do not act to seal the hoseacross the fold. This has been found to be a significant defect of suchhose not having a "NETLON" or similar insert to maintain a passage ofair or other working fluid between the two portions of the hose oneither side of the fold therein. On inflation of such inferior hosearrangements, a body of air becomes trapped in the portion of the hoseon the far side of the fold from the air supply pipe and consequentlycomplete deflation of the hose when required cannot take place.

In use the motorized joint of FIGS. 7 and 8 operates on selectiveconnection of air supply and vent pipe 97 to a pressurized air supply(not shown) which supplies air under pressure to the interior ofinflatable hose 95 having "NETLON" sheet 102 inserted therein.Inflatable hose 95 therefore inflates and simultaneously tends torelieve the fold therein, and both these effects result in forces whichreact at the clamp arrangement 90, against the outer surface of limb 83;and against flexible, inelastic strap 100 to create tension in the strap100. This tension reacts at clamping arrangement 101 to causeanticlockwise rotation of limb 84 and hence output shaft 80. Outputshaft 80 can be connected to an artificial limb such as an arm such thatthe motorized joint of FIGS. 7 and 8 can mimic the action of a humanshoulder in one plane of rotation.

Deflation of inflatable hose 95 on selective connection of pipe 97 to aventing arrangement, not shown in FIGS. 7 and 8, but which generallycomprises the vent part of a solenoid actuated pneumatic control valve,generally results in reversal of the rotation of the output shaft 80under the self weight of the limb attached thereto; however, it may benecessary to provide a return spring 502 interconnecting limb 84 andeither the framework 82 or fixed limb 83. A suitable type of spring is atension spring known as a TENSATOR spring.

Alternatively, the motorized joint of FIGS. 7 and 8 can be built in atandem configuration, having two inflatable elements each selectivelyconnectable to a pressurized air supply to produce rotation of theoutput shaft in respectively opposite directions.

Strap 100 may be secured to limb 84 to cause clockwise rotation thereofon inflation of the hose 95.

A fourth preferred embodiment of the present invention is shown in FIG.9. The motorized joint of FIG. 9 comprises a pair of circular, hollowskeletal limbs 110, 111 interconnected by a joint 112 permittingrelative rotation of limbs 110 and 111 to one another about their commonlongitudinal axis, while preventing relative movement between the limbs110 and 111 in the longitudinal axial direction. Bearing arrangementsfor such joints are well known in the art and generally compriseinternally mounted roller bearings to permit relative rotation of thelimbs acting in conjunction with two or more internal thrust bearingmeans to prevent relative axial movement of the limbs.

Interconnecting limbs 110 and 111 is an inflatable element 14 in theform of an inflatable hose 114 having inelastic walls and which isfolded in a helical fashion around the outer circumference of circularlimbs 110 and 111 to be secured at each end 115, 116 respectivelythereof to the limbs 110 and 111. The end 115 of hose 114 is secured toskeletal limb 110 by clamping means 120 as shown in FIGS. 2 and 3. Thus,an air supply and vent pipe 122, which is selectively connectable toeither a pressurized air source or a venting arrangement respectively,communicates with the interior of inflatable hose 114. Pipe 122 isretained in position by the clamping means 120 which also seals end 115of inflatable hose 114 about pipe 122. End 116 of inflatable hose 114 issecured to limb 111 and sealed against escape of air under pressure byclamping means 124. Clamping means 124 is of the type similar to thatshown in FIGS. 2 and 3 but which does not incorporate provision for anair supply and vent pipe.

Inflatable hose 114 comprises an elongate sheet (not shown in FIG. 9) of"NETLON" inserted along the interior length thereof to ensure that thereis a passage for the flow of air along the hose 114 at all times duringthe inflation and deflation thereof.

When air supply and vent pipe 122 is connected to a pressurized airsupply source (not shown) the inflatable hose 114 inflates and tends torelieve the folding therein. The inflation of hose 114 tends in additionto shorten the distance between the ends 115 and 116 thereof due to theexpansion of hose 114 drawing the average center line thereof away fromthe circumference of the limbs 110 and 111. The effects of expansion ofhose 114 and the tendency of said hose to unfold on expansion results inrotation of limb 111 relative to limb 110 in the direction of arrow A inFIG. 9. Deflation of inflatable hose 114, which deflation is caused byselective connection of air supply and vent pipe 122 to a ventingarrangement (which in practice is the vent port of a solenoid actuatedpneumatic control valve) results in the effects referred to aboveoccurring in an opposite sense to that in which they occur on inflationof inflatable hose 114 and consequently rotation of limb 111 relative tolimb 110 in an opposite direction to that indicated by arrow A occurs.If necessary, however, a return spring 503 arrangement may be employedto assist in the operation of the motor driven joint on deflation of theinflatable hose 114. Such a return spring 503 may conveniently be atorsional spring or torsional member, such as a whalebone shaft,interconnecting the interiors of the two hollow, cylindrical, skeletallimbs 110 and 111 to provide a torsional return force.

The embodiment of the invention shown in FIG. 9 may conveniently be usedas a wrist joint in artificial limbs, both in models and surgicalprostheses; or as a neck joint simulating animal neck movements inanimated models. In the latter case, two such joints would be connectedin series to provide positive rotational movement of an animal head bothto the left and to the right.

FIGS. 10 and 11 show a fifth preferred embodiment of the presentinvention. FIG. 10 is a top plan view of a backing plate 200 havingtransverse slots 202, 204 cut at either end respectively. A flexible,inelastic strap 206 is threaded from the underside of backing plate 200through slot 202 to pass over the upper surface of folded, inflatablehose 210 which is similarly arranged to that in the embodiment of theinvention shown in FIG. 6. Both ends of inflatable hose 210 are clampedby clamping means 212 which is identical with the arrangement shown inFIGS. 4 and 5. One end of strap 206 is secured in clamping means 212while the other end thereof, which is disposed on the underside ofbacking plate 200 comprises an eye 220 which, in use, engages a hookdisposed on a skeletal limb not shown in FIGS. 10 and 11. Passingthrough, and secured about slot 204 is a second strap 222 having at thefree end thereof a second eye 224 which, in use, engages a hook on asecond skeletal limb (not shown). Air supply and vent pipe 226communicates with the interior of inflatable hose 210 and is selectivelyconnectable to either a pressurized air supply source or a ventingarrangement as in embodiments of the invention described hereinabove. Inuse, inflation of inflatable hose 210 by connection of supply pipe 226,which is sealingly retained in the open end of the inflatable hose byclamping means 212 as shown in FIGS. 4 and 5, to an air supply source,results in expansion and straightening of the hose which, by virtue offorces reacting at clamping means 212 and against backing plate 200,create tension in strap 206. If eye 220 and eye 224 are respectivelyattached to separate, relatively movable limbs of a motorized joint (notshown in FIGS. 10 and 11) the tension in strap 206 will be transferredvia second strap 222 and eyes 220 and 224 to operate the joint in amanner similar to that of the embodiment of the invention shown in FIG.6. The embodiment of FIGS. 10 and 11 is therefore an embodiment of theinvention which can be installed temporarily in a joint and subsequentlyremoved without necessitating complete dismantling of the joint.

FIG. 12 is a representation of a length of the inflatable hose used toform the inflatable element of all the embodiments of the inventiondescribed above. The hose comprises an inner neoprene tube 150 coveredwith and bonded to a fibrous webbing sheath 152. It will be clear fromFIG. 12 that the hose, when deflated, is of generally flat transversecross-section. The hose, however, will tend to adopt a circularcross-section on inflation and this arrangement allows a significantforce due to expansion to be obtained from an essentially inextensiblehose.

A flexible, flat sheet 154 of nylon mesh netting, such as "NETLON" isinserted within the hose and serves to maintain a passage for the flowof air or other fluid through the hose no matter how severely folded orkinked the hose may become. This effect is achieved by the opposinginterior faces of the neoprene tube 150 being prevented at all timesfrom meeting fully and hence sealing the pipe in the vicinity of astrand of the mesh.

Clearly, any filament-like feature preventing full closure of theneoprene tube 150 would have a similar effect to that of the nylon mesh.Examples of such filament-like features include raised contours mouldedon the interior faces of the neoprene tube, or lengths of nylon twine orsimilar material inserted into the tube. However, the use of a flexiblemesh has significant advantages over such alternative methods since asheet of nylon mesh, of appropriate dimensions, is generallyself-centering in the neoprene tube; and further the cost of a mesh suchas "NETLON" is low while maintaining adequate durability.

FIGS. 13 to 15 inclusive of the drawings are schematic representationsof simple pneumatic or hydraulic arrangements which may be used as partof a control circuit for motorized joints of the kinds describedhereinabove.

FIG. 13 shows a simple 3-port 2-position solenoid actuated valve 170,which valves are well known in the art, and which may have the supplyport 172 thereof selectively connected to either a pneumatic orhydraulic main 174 or a vent port 176 by virtue of the position of thesolenoid actuator. The output supply port 172 is connected to an airsupply and vent pipe of a motorized joint according to the invention andthrough which the inflatable element may be either inflated or deflatedas desired.

FIG. 14 shows a 5-port, 2-position solenoid actuated valve 180, which isused similarly to the valve of FIG. 13 for controlling a pair ofmotorized joints according to the present invention. The joints arerespectively connected to an air supply 188, according to the positionof valve 180, by respective pipes 182 and 184. When one of the joints isconnected to air supply 188, the other is connected to a vent port 186,and vice versa. The pair of motorized joints may be arranged in aconfiguration permitting opposed operation of the joints using the valveof FIG. 14.

FIG. 15 shows a simple proportional control circuit comprising a pair190, 194 of 3-port, 2-position solenoid actuated valves arranged tooperate with a pressure switch 192 to provide proportional inflation andventing of the inflatable members via pipes 191 according to the settingof pressure switch 192.

It will be appreciated that all the pneumatic circuits referred tohereinabove can equally well be arranged to operate with a hydraulicworking fluid.

The embodiments described hereinabove represent the essential featuresof artificial limbs to be constructed in accordance with the invention.It will be clear that, for complete realism of appearance and movementof limbs so constructed, the motorized joints described above arecovered in some material resembling human or animal flesh, skin andwhere necessary, fur. When so covered, the motorized joints of theinvention have an extremely realistic appearance since, in use, movementof the motorized joint results in an apparent flexing or tensing of theartificial muscle comprised within the joint. This feature, coupled withthose of low internal friction referred to above, creates a whollyconvincing appearance and action in the artificial limbs comprisingmotorized joints of the present invention. Suitable materials forcovering the motorized joints include a number of proprietary andspecialized foamed rubbers and plastics, along with semi-elastic plasticouter coverings to represent animal or human skin A wide variety ofphysical features of appearance can therefore be incorporated within thelimb, adding to the effects of realism created therein. Such featureshave many advantages, both in producing lifelike models forhigh-technology television and film recordings, and in alleviating manyof the psychological disadvantages suffered by some recipients ofartificial limb prostheses.

Finally, it will be clear that the applications of the motorized jointof the present invention extend beyond those described above. There aremany instances in the field of industrial robotics, for example, whereit is advantageous to have a robot arm capable of moving in a number ofnon-parallel planes using motors having very low internal friction, withthe motors also being highly amenable to proportional control. Suchrobot arms can easily be constructed, at very low relative cost, usingthe principles of the invention described herein.

We claim:
 1. A motorized joint comprising a pair of relatively movablemembers; an elongate, inflatable element having an inextensible wall;means for holding apart opposing inner surfaces of the inflatableelement such that a fluid passage exists within the inflatable element;actuating means having means for inflating the inflatable elementcausing it to increase in cross section; and means mounting the two endsof said inflatable element in a folded condition on one of therelatively movable members and acting on the other relatively movablemember whereby inflation of the inflatable element causes relativemovement between the relatively movable members.
 2. A motorized jointaccording to claim 1 wherein the relatively movable members are mountedfor relative rotation about parallel axes, and further including meansfor transmitting a force resulting from inflation of the inflatableelement to the other relatively movable member to effect relativerotation of the relatively movable members.
 3. A motorized jointaccording to claim 2, wherein the relatively movable members are mountedin a framework interconnecting each other and permitting relativerotation therebetween.
 4. A motorized joint according to claim 1 whereinthe inflatable element comprises a length of inflatable, hollow hosesealed at one end and unsealed at the other end and having a generallyflat transverse cross section when in a deflated state.
 5. A motorizedjoint according to claim 4 wherein the means to inflate the inflatableelement comprises means to supply fluid under pressure to the interiorof said inflatable element, said supply fluid means including a fluidsupply pipe retained in an aperture at the unsealed end of theinflatable element; at least one sealing block means adapted to sealsaid unsealed end of the inflatable element having the fluid supply piperetained therein; clamping means to press said sealing block means intocontact with said ends of the inflatable element against a reactionsurface also adapted to accommodate said ends of the inflatable element;pressurized fluid supply means selectively connectable to said supplypipe to supply inflating fluid thereto; and venting means selectivelyconnectable to said supply pipe for use in deflating said inflatableelement.
 6. A motorized joint according to claim 1 further comprisingmeans for securing the inflatable element to at least one of saidrelatively movable members, said means for securing including clampingmeans for securing the inflatable element to at least one of saidrelatively movable member.
 7. A motorized joint according to claim 1wherein the means for holding apart opposing inner surfaces of theinflatable element comprises a length of flat, flexible, moulded plasticnetting of narrow width than the narrowest transverse dimension of theinflatable element when inflated, said length of netting being insertedlengthwise in said inflatable element to maintain separation of opposinginner surfaces of the inflatable element on collapsing of saidinflatable element on deflation, folding and kinking thereof.
 8. Amotorized joint according to claim 1 further comprising spring meansinterconnecting the relatively movable members, said spring means, ondeflation of the inflatable element, causes reversal of the movementbetween the relatively movable members.
 9. A motorized joint accordingto claim 1 further comprising a pneumatic circuit arranged to controlinflation and deflation of the inflatable element.
 10. A motorized jointaccording to claim 1 further comprising an hydraulic circuit arranged tocontrol inflation and deflation of the inflatable element.